The proof of concept uses Forsyth–Edwards Notation (FEN) for the off-screen password field submitted by the form. A FEN string is a combinations of numbers, slashes dashes, uppercase and lowercase letters:

rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2

Alternatively, a user could be prompted to enter a number of moves on the board and the Portable Game Notation (PGN) string could be used for the password:

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 ...

Passwords could be made even stronger by insisting the user makes a minimum number of moves on the board.

From a security perspective, both of these options look pretty good and a chess player might find it more memorable than a traditional password field.

It's certainly an interesting idea. If implemented in the right way and in the right scenario, a chess website perhaps?, it might be a nice alternative to a traditional password field.